1. Field of the Invention
The present invention relates generally to a method of manufacturing a semiconductor device. More particularly, the present invention relates to a method of manufacturing a semiconductor device capable of obtaining a higher static capacity and a lower leak current characteristic, which first forms a tantalum oxide film and then performs a plasma process, and second controls a source to be injected in the last step of forming a tantalum oxide film, thus forming a tantalum oxy-nitride film.
2. Description of the Prior Arts
Recently, tantalum oxide Ta2O5 becomes used widely as a dielectric film of a capacitor having more than 256M DRAM device. The tantalum oxide film is higher 5 times in the dielectric constant than an ONO film (Oxide-Nitride-Oxide), which is used as a dielectric film of a capacitor in the existing process of manufacturing DRAM. Thus, the tantalum oxide film has become widely used as dielectric film materials of the capacitor in the process of manufacturing DRAM that requires a higher integration. Further, Ta2O5 can provide a high step coverage if it is processed by CVD process. Also, Ta2O5 may have a good dielectric characteristic and can be implemented as a less current film, if a subsequent annealing process processes it. Recently, there has been an attempt to reduce the thickness of an effective oxide film of the capacitor to 17 angstrom, in which tantalum oxide is used as the dielectric film using tungsten as a lower electrode.
In this case, the annealing process must be performed under the oxidization atmosphere in order to remove impurities within the tantalum oxide, but it can not performed sufficiently at higher temperature since tungsten forming the lower electrode will be oxidized. Due to this, it is difficult to completely remove the impurity within the tantalum oxide film. Thus, there is a problem that the leak current of the capacitor using the tantalum oxide film as the dielectric film can be increased. Also, there is a high possibility of deteriorating the electrical characteristic of the capacitor since the amorphous tantalum oxide film may react with the titanium nitride film during the process of depositing the titanium nitride film to be an upper electrode by CVD method.
It is therefore an object of the present invention to provide a method of manufacturing a capacitor in a semiconductor device capable of improving the leak current and the electrical characteristic.
In order to accomplish the above object, the method of manufacturing a capacitor in a semiconductor device according to the present invention is characterized in that it comprises the steps of forming a lower electrode on a semiconductor substrate in which a given lower structure is formed; forming a first tantalum oxide film on the lower electrode and then performing a plasma process to it; forming a second tantalum oxide film and then forming a tantalum oxy-nitride film; and forming an upper electrode on the tantalum oxy-nitride film.